The present invention relates to a lightning resistive device for preventing lightning damage in an aerial power transmission system by connecting lightning arresters on a steel tower supporting aerial power transmission cables.
In the conventional aerial power transmission system, an aerial ground wire is suspended on tops of steel towers to protect the power transmission cables supported on the steel towers by insulators from lightning damage. In such a system, lightnings are collected to the aerial ground wire and the power transmission cables are protected from the direct lightning in the shielding angle of the aerial ground wire.
However, in such a conventional system, when lightning energy to the aerial ground wire is too large, a potential of the steel tower is suddenly raised to cause reverse flashover to the power transmission cable whereby a grounding fault may be caused.
In order to prevent the lightning damage, it has been proposed to connect lightning arresters between the power transmission cables and the ground to reduce the lightning damage in some districts. However, it has been difficult to prepare lightning arresters durable to direct lightning from the technological viewpoint and effect for preventing the lightning damage of the power transmission cables has not been substantially expected.
Recently, excellent non-linear resistors of sintered products prepared by sintering a composition of a main component of zinc oxide and the other minor component at high temperature, have been developed. Therefore non-dynamic current type lightning arresters for power transmission system could be obtained by using such non-linear resistor, whereby an operation duty to the direct lightning of about 100 KA could be expected.